The Tech Model Railroad Club at MIT, one of the wellsprings of
hacker culture. The 1959 Dictionary of the TMRC
Language compiled by Peter Samson included several terms that
became basics of the hackish vocabulary (see
esp. foo, mung, and
frob).

By 1962, TMRC's legendary layout was already a marvel of complexity
and has grown in the years since. All the features described here were
still present when the old layout was decommissioned in 1998 just before
the demolition of MIT Building 20, and will almost certainly be retained
when the old layout is rebuilt (expected in 2003). The control system
alone featured about 1200 relays. There were scram
switches located at numerous places around the room that could
be thwacked if something undesirable was about to occur, such as a train
going full-bore at an obstruction. Another feature of the system was a
digital clock on the dispatch board, which was itself something of a wonder
in those bygone days before cheap LEDs and seven-segment displays. When
someone hit a scram switch the clock stopped and the display was replaced
with the word ‘FOO’; at TMRC the scram switches are therefore
called foo switches.

Steven Levy, in his book Hackers (see the
Bibliography in Appendix C), gives a
stimulating account of those early years. TMRC's Signals and Power
Committee included many of the early PDP-1 hackers and the people who later
became the core of the MIT AI Lab staff. Thirty years later that
connection is still very much alive, and this lexicon accordingly includes
a number of entries from a recent revision of the TMRC dictionary.